Optimization Design Method Of Low-noise Diesel Engine Composite Structure And Connection Parts

As people's standard is improving constantly, the quantity of possession of automobiles is substantially increasing and people's requirement for comprehensive performance of automobiles is also enhanced continuously. The research for NVH technology has been one of the main subjects in the research area of cars. Noise reduction is one of the highest challenging targets for ICE development. In order to enhance the level of study on the noise and vibration of ICE, this dissertation mainly focused on the following items in depth and meticulous:the study on engine noise and vibration predict method,numerical simulation method of connection parts,low-noise engine structural optimization design,which integrate multiple methods, such as theory, experiment and virtual design.In the aspect of numerical simulation methods of connection parts,this paper mainly studied two numerical simulation methods of connection parts: linearity method that considered bolt preloading and gaskets, and nonlinearity method that used contact element. Those two methods had been used to simulate the gasket and the preload of the bolts in the transient vibration analysis. On that basis; introduce the linearity method used in the transient vibration analysis of ICE. The comparisions of results between the calculation result and the experimental result show that the linearity method can accurately calculate the vibration severity of ICE.In the aspect of low-noise engine structural optimization design, there are 3 methods: the analyses of vibration and radiated noise that influenced by reinforcing plate for the 6 in-line engines; a new kind of gasket that shape of cross section is T-shaped; and single balanced shaft scheme of vertical 4 cylinder diesel engine.A reinforcing post has been used to reduce the vibration and radiated noise of 6 in-line engines. The mode of cylinder body with reinforcing plate and without that are analyzed through the method of finite element.The result shows that the reinforcing post may help to increase the natural frequency and then improve the stiffness of cylinder body. The test results shows that the reinforcing post can help to lower the vibration of the cylinder,and finally reduce the radiated noise.Introduce a new kind of cylinder head cover gasket that shape of cross section is T-shaped. Calculate the vibration attenuation of the T-shaped and the ordinary gasket show that the T-shaped gasket can effectually reduce the vibration of cylinder head cover. The T-shaped gasket was verified by test. According to the results of noise and vibration test, the T-shaped gasket is better then ordinary gasket and that and be used in the ICE.At last ,based on analyzing the balance of 4-cylinder engine,it is concluded that the exciting source includes secondary inertia force and inner moment.Use the single balanced incomplete balance scheme can not only balance a part of the secondary inertia force, but also reduce the inner moment, so as to reduce the vibration intensity. Finally, optimum balance scheme that use the single balanced shaft balance 20% of the secondary inertia force is decided.